[There's a hint of irritation at Ratchet's outburst, but he isn't necessarily wrong.]

We don't know what Megatron would be able to accomplish with the Matrix or how much of its power he may be able to wield. Allowing him to take the Force unchallenged was not a risk worth taking.

If we possessed the Forge it would be to our benefit should the restoration of the Matrix allow Orion the power of the Primes once again.